The adaptive significance of circadian singing rhythms of the cricket, Teleogryllus oceanicus, in nature after cold spells, and the influence of a lunar cycle upon calling activity will be studied. The possibility of extracephalic photoreceptors and clocks generating the oviposition rhythm of the grasshopper, Chorthippes curtipennis will be investigated. Daily periodicity in juvenile hormone (JH) synthesis by the corpora allata (c.a.) in the cricket, Teleogryllus commodus, under fluctuating environmental conditions will be measured using a radiochemical assay. C.a. activity in vitro during ovarian maturation will be studied with the same method. The JH titer of the hemolymph increases after mating. The regulatory mechanism will be studied by interfering with nervous, hormonal and neuroendocrine pathways connecting the reproductive system with the c.a., and by determining the titer following the operations. In the female grasshopper, Syrbula fuscovittata, whose reproductive behavior is under the control of the c.a., the behavioral switch from the unreceptive state to sexual readiness can be accelerated by prolonged male-courtship. This sensory stimulation might cause a sudden increase in JH synthesis by the c.a., and their activity will be measured with the radiochemical assay. Target organs of prostaglandin E2 (PG) stimulating cricket oviposition include the oviducts and the last abdominal ganglion. Muscular and nervous activity will be recorded before and after perfusion with PG. The hypothesis that the PG-precursor arachidonic acid is biosynthesized from linoleic acid will be tested by incubating diverse tissues with Na(1-14C)-acetate. The role of phospholipase A2-activity in the liberation of phospholipid-bound arachidonic acid in the female's spermatheca will be studied. Degradation pathways of PGs will be followed. The function of multiple mating to increase egg production will be examined, in particular sperm competition for egg fertilization by means of radiolabelling nucleic acids in sperm.